Java Magazine - January/February 2012

Project Coin: The Java Language
Has Evolved!
JULIEN PONGE
Three additions to the Java language in Java SE 7 will help you be more productive.

JAVA IN ACTION

Project Coin is an OpenJDK project that initiated the Java language changes that were standardized as part of Java SE 7 under JSR-334 in the Java Community Process (JCP). The project is self-described as follows:

“The goal of Project Coin is to determine what set of small language changes should be added to JDK 7. That list is:

■ ■ Strings in switch

■ ■ Binary integral literals and underscores in numeric literals

■ ■ Multi-catch and more precise rethrow

■ ■ Improved type inference for generic instance creation (diamond)

■ ■ try-with-resources statement

■ ■ Simplified varargs method invocation”

This article is the first in a two-
part series covering each item
of Project Coin. The goal is to
present the immediate usage of
each feature, and also to provide
some background on the impli-
cations for implementing each
of them, especially since they all
maintain backward compatibil-
ity with prior versions of Java SE.
The impact of each change was
remarkably balanced
with a scientifically
sound analysis of mil-
lions of lines of existing
Java code.

/* The value 123 in decimal,
octal and hexadecimal */
byte decimal = 123;
byte octal = 0173;
byte hexadecimal = 0x7b;

by a combination of zeros and ones up to the size of the underlying primitive type. The decimal number 123 can be written as the following binary literal:

// 123 in binary byte binary = 0b01111011;

Java SE 7 allows
strings to be
used in switch
statements.

The rules are simple. A decimal
number is a literal comprising a
combination of digits between
0 and 9, an octal number starts
with a zero, and a hexadecimal
number starts with 0x. With the
advent of Java SE 7, you can now
specify a number as a binary lit-
eral by starting it with 0b followed
If fewer digits are provided than
expected for the underlying primi-
tive type, the missing digits are
considered to be at the beginning
of the representation, and they
are given a value of zero. Thus, the

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PHOTOGRAPH BY MATT BOSTOCK/GETTY IMAGES

Binary Integral Literals and Underscores Prior to Java SE 7, numeric literals could be specified either in decimal, octal, or hexadecimal forms, such as in the following: